The need often arises to transport an object inside or along an elongate passage that is unsuitable for human entrance due to size constraints or safety concerns. This situation for instance occurs in the mining environment when ore passes become obstructed.
An ore pass is a passage drilled between parallel upper and lower tunnels in a mine. In use ore is deposited into the upper end of the ore pass that extends downwardly from the bottom wall of the upper tunnel. The lower end of the ore pass, extending upwardly from the top wall of the bottom tunnel, is closed by means of a steel door, thus causing the ore to accumulate inside the ore pass. When required, the door is opened so as to deposit the ore in the ore pass into trucks located below the lower opening of the ore pass. This configuration serves to effectively remove ore in an environment where space is of utmost concern, as it will be difficult, if not impossible, to load ore into a truck located in the same tunnel as the ore.
The abovementioned method works well, but from time to time an ore pass tends to block due to ore becoming stuck therein. Due to the nature of these blockages the ore pass is usually opened by blasting the ore pass open using an explosive charge, thus dislodging the obstructing ore.
A number of methods have previously been utilized to load the explosive charge into the ore pass. In one example a person climbs into the ore pass and pushes the explosive charges towards the blockage using a specially designed cart. A further option is to shoot the explosive charge into the ore pass using a compressed air catapult device. In both cases the explosive charge is then detonated once the personnel involved in the operation have been evacuated. However, in both cases substantial manual intervention is required, and the method is also not as controlled as is desirable when working with explosives. These methods have therefore been declared unsafe mining practices by safety authorities.
A safer option is to utilize radio controlled vehicles to convey the explosive charge into the ore pass. However, ore passes are often orientated at steep inclinations, thus rendering the use of these radio controlled devices impractical due to loss of traction at acute angles.
Due to the lack of cost-efficient yet safe solutions to this problem, the preferred option is often to leave the ore pass in the blocked condition, and to drill a new ore pass adjacent the blocked ore pass. It will be appreciated that valuable ore is lost in this manner, and that considerable expenses are incurred in drilling new ore passes.